diff --git a/Doc/tutorial/classes.rst b/Doc/tutorial/classes.rst
--- a/Doc/tutorial/classes.rst
+++ b/Doc/tutorial/classes.rst
@@ -337,6 +337,74 @@
 argument list.
 
 
+.. _tut-class-and-instance-variables:
+
+Generally speaking, instance variables are for data unique to each instance
+and class variables are for attributes and methods shared by all instances
+of the class:
+
+    class Dog:
+        
+        kind = 'canine'       # class variable shared by all instances
+
+        def __init__(self, name):
+            self.name = name  # instance variable unique to each instance
+
+    >>> d = Dog('Fido')
+    >>> e = Dog('Buddy')
+    >>> d.kind                # shared by all dogs
+    'canine'
+    >>> e.kind                # share by all dogs
+    'canine'
+    >>> d.name                # unique to d
+    'Fido'
+    >>> e.name                # unique to e
+    'Buddy'
+
+As discussed in the section above, ``A Word About Names and Objects``, shared
+data can have possibly surprising effects with involving :term:`mutable`
+objects such as lists and dictionaries.  For example, the *tricks* list in the
+following code should not be used as a class variable because just a single
+list would be shared by all *Dog* instances:
+
+    class Dog:
+        
+        tricks = []       # mistaken use of a class variable
+
+        def __init__(self, name):
+            self.name = name
+
+        def add_trick(self, trick):
+            self.tricks.append(trick)
+
+    >>> d = Dog('Fido')
+    >>> e = Dog('Buddy')
+    >>> d.add_trick('roll over')
+    >>> e.add_trick('play dead')
+    >>> d.tricks              # unexpectedly shared by all dogs
+    ['roll over', 'play dead']
+
+Correct design of the class should use an instance variable instead:
+
+    class Dog:
+
+        def __init__(self, name):
+            self.name = name
+            self.tricks = []       # new empty list for each dog
+
+        def add_trick(self, trick):
+            self.tricks.append(trick)
+
+    >>> d = Dog('Fido')
+    >>> e = Dog('Buddy')
+    >>> d.add_trick('roll over')
+    >>> e.add_trick('play dead')
+    >>> d.tricks
+    ['roll over']
+    >>> e.tricks
+    ['play dead']
+
+
 .. _tut-remarks:
 
 Random Remarks